A. Pull over to the left before you reach the intersection.
You are approaching a green light in vehicle A. An ambulance sounding its siren is approaching the same intersection and has a red light. You should:
A. Pull over to the left before you reach the intersection.
B. Slow down and stop if necessary to prevent getting in its way.
C. Keep driving because you have the green light.
Ambulances have ambulance written in reverse on the front so that you can read it in your rear-view mirror.
If you are waiting at an intersection the ambulance driver will find a way through. Don't emerge into the intersection unless the ambulance waits behind you, and only emerge on a green light, not a red light. If you go through into the intersection you could receive a red light camera fine, and you put yourself in danger of being hit by other vehicles in the intersection. Emergency services drivers are trained not to pressure a driver into doing something dangerous.
If you have a green light and you are waiting and hear an ambulance at the intersection approaching from a road that has a red light, you must stop and wait until the ambulance has passed through the intersection. There could be one or more emergency vehicles, especially if it's a fire engine (a large fire might require two or more vehicles).
More information about emergency vehicle sirens.